Selection doesn't always redraw when resizing the window (canvas renderer)

[Tyriar]

Repro:

1. Make a selection
2. Resize the window

Sometimes the selection will show, sometimes not.

[Tyriar]

Selection is drawn here for the canvas renderer: https://github.com/xtermjs/xterm.js/blob/master/src/renderer/SelectionRenderLayer.ts

[khoitd1997]

I will tackle this one